Multiple portion packaging tray and method of making same

ABSTRACT

A multiple portion packaging tray comprising a plurality of pliable polymer containers configured in an array, each comprising a receptacle and an integral peripheral flange extending from the receptacle, the flanges integrally connecting adjacent containers to one another along perforation lines comprising a series of alternating openings and land areas wherein the land areas are sized so that the containers are separated by tearing apart the flanges without propagating cracks across the flanges. The method of making a multiple portion packaging tray in a former comprising a form station and a separate trim station comprising the steps of thermoforming the multiple portion packaging tray and cutting the perimeter and perforation lines of the multiple portion packaging tray to create a series of alternating openings and land areas.

FIELD OF INVENTION

This invention relates to plastic containers for use in packaging. Inparticular, this invention relates to packaging comprising an array ofseparably connected plastic containers that are easily separated andmethods of making such containers.

BACKGROUND OF INVENTION

Use of single serve plastic containers is well known in the food productindustry. These single serve containers are sometimes manufactured andsold in a multiple portion packaging tray comprising an array ofseparable containers. The containers are generally connected to oneanother along their flanges and may be broken apart by breaking theconnection at the flanges. These containers work well when made of arelatively brittle plastic. Use of less brittle or more pliable polymersmakes the containers more difficult to break apart. For some foods,brittle plastics, such as polystyrene, cannot provide the necessaryprotection and a high moisture barrier polymer is needed, such aspolypropylene or polyethylene. Polypropylene and polyethylene are alsogenerally lower cost materials than polystyrene. Traditionally, singleserve packages made from polyolefins include secondary packaging, suchas a cardboard sleeve, to form a multiple portion package. Connectingindividual containers to form a multiple portion packaging without theuse of secondary packaging, however, would deliver a substantial costbenefit. Accordingly, there is a need for an array of separablyconnected plastic containers made from less brittle and more pliablepolymers.

Containers in the form of an array of separably connected plasticcontainers are typically formed from thermoforming processes well knownto those of skill in the art. Examples of such thermoforming methodsinclude solid phase pressure forming, melt phase forming, plug assist,vacuum forming, and drape forming. After thermoforming, the containersare transferred to a separate trim station, outside of the thermoformingstation, to trim the containers.

SUMMARY OF INVENTION

This invention addresses the above-described need by providing amultiple portion packaging tray comprising a plurality of pliablepolymer containers configured in an array. Each pliable polymercontainer comprises a receptacle and an integral peripheral flangeextending from the receptacle, the flanges integrally connectingadjacent containers.

More particularly, this invention comprises perforation lines in theflanges as a means to easily separate the containers. The perforationlines comprise a series of alternating openings and land areas whereinthe land areas are sized so that the containers are easily separated bytearing apart the flanges without propagating cracks across the flangesor compromising the containers' integrity and at the same time arerobust enough to survive normal handling in a distribution process without separating incidentally.

In addition, this invention encompasses a method for making a multipleportion packaging tray comprising a plurality of pliable polymercontainers configured in an array. This method is performed in a formercomprising a form station and a separate trim station and comprises thesteps of thermoforming a pliable polymer sheet in the form station tocreate the multiple portion packaging tray and cutting the flanges inthe trim station to form perforation lines having a series ofalternating openings and land areas.

Other objects, features, and advantages of this invention will beapparent from the following detailed description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an array of separably connected plasticcontainers in accordance with an embodiment of this invention.

FIG. 2 a is a partial elevation view of the embodiment in FIG. 1illustrating a perforation line.

FIG. 2 b is a partial plan view of the embodiment in FIG. 1 illustratinga perforation line along its longitudinal length.

FIG. 3 is a schematic representation of a system of making an array ofseparably connected plastic containers in accordance with an embodimentof this invention.

FIG. 4 is an exploded schematic representation of a trim station used inthe embodiment illustrated in FIG. 3.

FIGS. 5 a and 5 b are elevation views of notched steel rule knives usedin the embodiment illustrated in FIG. 3.

DETAILED DESCRIPTION

As summarized above, this invention encompasses a multiple portionpackaging tray comprising a plurality of pliable polymer containersconfigured in an array. Such containers are frequently used to packageindividual servings of food products, although other uses are well knownin the art. The containers are easily separable from the multipleportion packaging tray through the exertion of tensile force by hand.Embodiments of this invention are described in detail below andillustrated in FIGS. 1-5.

A multiple portion packaging tray 10 made in accordance with anembodiment of this invention is illustrated in FIG. 1. The multipleportion packaging tray 10 comprises a plurality of pliable polymercontainers 12 configured in an array. The individual containers 12comprise receptacles such as cups 14 surrounded by peripheral flanges16. The flanges 16 integrally connect adjacent containers 12 to oneanother. The flanges 16 comprise perforation lines 18 wherein theperforation lines provide a means to easily separate the individualcontainers 12 from the multiple portion packaging tray 10. Theperforation lines 18 may be formed within channels 19 formed in theflanges 16, as shown in FIGS. 1, 2 a and 2 b, or directly innon-channeled flanges. The channels 19 can be formed by any suitablemeans including but not limited to coining, and the like. Theperforation lines 18 comprise a series of alternating openings 20 andland areas 22. The land areas 22 are sized so that the individualcontainers 12 are easily separated by tearing apart the flanges 16 atthe tear lines 18 using tensile forces without propagating cracks acrossthe flanges 16. Desirably, the land areas 22 can be easily pulled apartby hand yet are strong enough to survive normal handling and shipping.The perforation lines 18 extend along the flanges 16 in a longitudinaldirection D as illustrated in FIG. 2 b. The length L of the land areas22 in the longitudinal direction D of the perforation lines 18preferably ranges from about 15 mils to about 32 mils, more preferablyfrom about 18 mils to about 22 mils. The length L of the land areas 22in the longitudinal direction D of the perforation lines 18 is mostpreferably about 20 mils.

The multiple portion packaging tray 10 preferably comprises a pliablepolymer material which is desirable in some packaging applications. Forexample, polyolefins are suitable pliable polymer materials for formingthe packaging tray 10. Preferred polyolefins include polypropylene, highdensity polyethylene, and low density polyethylene. The most preferablepolyolefin is polypropylene. The pliable polymers also may be coextrudedwith other materials. For example, polypropylene may be coextruded withethylene vinyl alcohol by using ethylene vinyl acetate based tie layersfor adhesion to the polypropylene. Other pliable polymer materials arealso suitable.

The thickness T of the pliable polymer can vary and is preferably atleast 3 mils and desirably ranges from 3 mils to about 40 mils, and moredesirable ranges from about 5 mils to about 30 mils. As illustrated inanother embodiment in FIG. 2 a, the flanges 16 may be coined to formchannels 19 so that the material thickness t at the perforation lines 18is less than or equal to that of the remaining portion of the flanges.

The method of making the multiple portion packaging tray 10 isillustrated in FIG. 3. The multiple portion packaging tray 10 can bemade using any suitable polymer sheet or film forming process, but isdesirably made using a thermoforming process 24. Suitable thermoformingmethods include solid phase pressure forming, melt phase forming, plugassist, vacuum forming, and drape forming. The thermoforming process 24occurs in a former 28 comprising a form station 30 and a separate trimstation 32. A pliable polymer sheet 26 is indexed through the formstation 30 to create the formed multiple portion packaging tray 10 usingthermoforming methods known to those skilled in the art. Desirably, themold temperature of the former 28 is controlled using cold water flowthrough internal channels in the mold to quench the formed multipleportion packaging tray 10 so that there is crystallization of thepolymer. The cooling process is well known to those of skill in the art.

The trim station 32, illustrated in an exploded schematic in FIG. 4,comprises steel rule knives 40 to cut the perimeter of the formedmultiple portion packaging tray 10. The trim station 32 furthercomprises notched steel rule knives 42 a and 42 b, best shown in FIGS. 5a and 5 b to create a series of alternating openings 20 and land areas22 in the longitudinal direction of the respective tear lines 18. Asillustrated in FIG. 5, the notched knives 42 a and 42 b comprisestandard straight blade steel rule knife material with notches 44 a and44 b sized to create land areas of a predetermined size so that theindividual containers 12 are easily separated by tearing apart theflanges 16 at the perforation lines 18 without propagating cracks acrossthe flanges 16. The perimeter knives 40 can also have small notches tocreate tabs attaching the multiple portion packaging tray 10 to thepolymer sheet 26. The steel knives 40 and 42 a and 42 b touch a strikerplate 46 to trim the perimeter of the multiple portion packaging tray 10and to create the openings 20 and land areas 22 of the perforation lines18. In another embodiment, the trim station 32 further comprises a punchand die system, well known to those of skill in the art, at the pointswhere the individual containers 12 meet on the multiple portionpackaging trays 10. The cutting by the steel knives 40 and 42 a and 42 band punch and die system may be done simultaneously or in separatesteps.

The multiple portion packaging trays 10 may be indexed to a stackingstation 36 where the perimeter tabs are broken by pushing the array ofcontainers 10 through the sheet 26 to a stacking chamber where they arecounted and pushed to a packaging station 38.

The present invention is further illustrated by the following example,which is not to be construed in any way as imposing limitations upon thescope thereof. On the contrary, it is to be clearly understood thatresort may be had to various other embodiments, modifications, andequivalents thereof which, after reading the description therein, maysuggestion themselves to those skilled in the art without departing fromthe spirit of the present invention and/or the scope of the appendedclaims.

EXAMPLE

A 30 mil 100% polypropylene sheet is used to make a multiple portionpackaging tray. The polypropylene sheet is heated to 160° C. as itindexes through an oven into the form station at 4 second cycles. In theform station, the hot sheet may be formed using a variety of methods.The formed multiple portion packaging tray leaves the forming station,still attached to the sheet. The formed multiple portion packaging trayenters the trim station approximately 8 seconds after leaving theforming station. At the trim station, a lower platen moves up to thesheet level to capture the individual containers in a die plate. Anupper platen containing steel rule knives, notched steel rule knives,and punches moves downward until it just touches the die plate and trimsthe perimeter of the multiple portion packaging tray as well as formsthe tear lines in the flanges with alternating opening and land areas.The notches of the notched steel rule knives are desirably 20 mils inlength. The upper and lower platens return to their initial positionsand the multiple portion packaging tray proceeds to the stackingstation. In the stacking station, a ram below sheet level pushes themultiple portion packaging tray up through the sheet, separating themultiple portion packaging tray from the sheet, and feeds the multipleportion packaging tray into a stacking chamber. The multiple portionpackaging trays are collected in the stacking chamber and pushed onto aconveyor for packing.

It should be understood that the foregoing relates to particularembodiments of the present invention, and that numerous changes may bemade therein without departing from the scope of the invention asdefined from the following claims.

1. A multiple portion packaging tray comprising a plurality of pliablepolymer containers configured in an array and each comprising areceptacle and an integral peripheral flange extending from thereceptacle, the flanges integrally connecting adjacent ones of thecontainers to one another along perforation lines in the flanges havinga series of alternating openings and land areas, wherein the land areasare sized so that the containers are separable by tearing apart theflanges without propagating cracks across the flanges.
 2. The multipleportion packaging tray as in claim 1 wherein the pliable polymercontainers comprise a polyolefin.
 3. The multiple portion packaging trayas in claim 2 wherein the polyolefin is polypropylene.
 4. The multipleportion packaging tray as in claim 2 wherein the polyolefin is highdensity polyethylene or low density polyethylene.
 5. The multipleportion packaging tray as in claim 2 wherein the pliable polymercontainers comprise a coextruded sheet comprising the polyolefin.
 6. Themultiple portion packaging tray as in claim 1 wherein each perforationline has a longitudinal direction and the length of each land area inthe longitudinal direction of the respective perforation line rangesfrom about 15 mils to about 32 mils.
 7. The multiple portion packagingtray as in claim 1 wherein each perforation line has a longitudinaldirection and the length of each land area in the longitudinal directionof the respective perforation line ranges from about 18 mils to about 22mils.
 8. The multiple portion packaging tray as in claim 1 wherein eachperforation line has a longitudinal direction and the length of eachland area in the longitudinal direction of the respective perforationlines is about 20 mils.
 9. The multiple portion packaging tray as inclaim 1 wherein the land areas have a thickness from about 3 mils toabout 40 mils.
 10. The multiple portion packaging tray as in claim 1wherein the land areas have a thickness from about 5 mils to about 30mils.
 11. The multiple portion packaging tray as in claim 1 wherein theflanges have channels and the perforation lines are formed in thechannels so that the thickness of the land areas is less than thethickness of the flanges outside of the channels.
 12. The multipleportion packaging tray as in claim 1 wherein the containers are made bythermoforming a pliable polymer sheet.
 13. The method of making amultiple portion packaging tray in a former comprising a form stationand separate trim station comprising the steps of: thermoforming apliable polymer sheet in a form station to create the multiple portionpackaging tray comprising a plurality of pliable polymer containersconfigured in an array and each comprising a receptacle and an integralperipheral flange extending from the receptacle, the flanges integrallyconnecting adjacent ones of the containers to one another; and cuttingthe flanges in the trim station to form perforation lines having aseries of alternating openings and land areas.
 14. The method as inclaim 13 wherein the step of cutting comprises cutting the flanges withsteel rule knives to trim the containers and cutting the flanges alongthe perforation lines with notched steel rule knives to form the openareas.
 15. The method as in claim 14 wherein the notches of the notchedsteel rule knives have a length that ranges from about 15 mils to about32 mils.
 16. The method as in claim 14 wherein the notches of thenotched steel rule knives have a length that ranges from about 18 milsto about 22 mils.
 17. The method as in claim 14 wherein the notches ofthe notched steel rule knives have a length of about 20 mils.
 18. Themethod as in claim 13 wherein the pliable polymer containers comprise apolyolefin.
 19. The method as in claim 19 wherein the polyolefin ispolypropylene.
 20. The method as in claim 19 wherein the polyolefin ishigh density polyethylene or low density polyethylene.
 21. The method asin claim 19 wherein the pliable polymer containers comprise a coextrudedsheet comprising the polyolefin.